Patent GB-813033-A (GB)
Title: Improvements in or relating to two-speed axle drive systems for vehicles
IPC: F16H63/30
Filed: 1957-03-21
Abstract: 813,033. Change-speed control. EATON AXLES Ltd. March 21, 1957 [April 4, 1956; Aug. 13, 1956], No. 9289/57. Class 80 (2). [Also in Group XXXVII] An axle drive system for a motor vehicle including a two-speed axle and a propeller shaft connecting the two-speed axle to the vehicle transmission comprises a ratio establishing member movable on change of ratio from driving engagement with a first part through a neutral position into driving engagement with another part, this movement being effected by means of a spring which is pre-loaded by motor means, a brake acting on the propeller shaft or the input to the two-speed axle whilst the ratio establishing member is in the neutral position during a change from low-speed ratio to high-speed ratio. In one form, change of ratio is effected by operation of a reversible electric motor 13, Fig. 1, under the control of a manually or automatically operated pre-selector switch 12. The motor 13 drives a shaft 42 on which is threaded a nut 44. A switch 40 is operated by the nut 44 to momentarily energize an eddy current brake 32 on the propeller shaft during a shift from low to high ratio, a conventional cut-out switch 18 also operated by the nut 44 switching off the motor 13 when the nut has reached the end of its travel in either direction. The nut 44, Fig. 2, is connected by a pin 46 to the forked end of a lever 52 connected to one end 60 of a coil spring 58, the other end 64 of which is in turn connected to a second lever 56 turnable about the same axis as the lever 54. The lever 56, Fig. 4, carries a grounded contact 88 which can be engaged with a triangular contact 84 pivoted at 86 on an insulated frame member. The triangular contact 84 carries an insulating pad 82 which normally prevents electrical contact between the triangular contact 84 and a spring blade 94 in a circuit leading through the eddy current brake 32. With the two-speed axle in low ratio, the parts take up the position shown in Fig. 5. To change to the high ratio, the motor vehicle driver moves the switch 12 to the highspeed position and thus causes the motor 13 to traverse the nut 44 along its shaft and turn the lever 52. If the driver keeps the vehicle accelerator pedal depressed, continued transmission of torque through the two-speed gear prevents the ratio establishing member, Fig. 3 (not shown), from moving and the lever 56, positively connected to the ratio establishing member, is likewise prevented from moving. Thus the spring 58 is stressed, and the levers 54, 56 take up the relative positions shown in Fig. 6. On release of the accelerator pedal by the vehicle driver, torque transmission ceases so that the pre-stressed spring 58 is able to turn the lever 56, and the associated ratio establishing member moves to the neutral position; simultaneously, the contact 88, Fig. 7, rolls the triangulated contact 84 into such a position that its corner 92 engages the spring contact 74 and completes the circuit through the eddy current brake 32. As soon as the speed of rotation of the driving and driven members of the highratio clutch in the two-speed axle have been synchronized, the eddy current brake 32 decelerating the speed of rotation of the propeller shaft to shorten the time taken before this occurs, the ratio establishing member moves to its high-ratio position, and the associated lever 56 moves to the position shown in Fig. 8. When changing from the high to the low ratio, the position of the insulating pad 82 on the triangular contact 84 is such that electrical contact is not made between the contacts 74, 84, so that the eddy current brake 32 is not energized. The brushing movement of the contacts 88, 84; 84, 74 ensures that electrical contacts are made between the parts, despite the presence of oil. In a modification, the motor 13, Fig. 9, traverses the nut 44 upon its shaft 42 to pre-tension a spring between the levers 52, 56 as before. The second lever 56 is formed with an extension 246 grounded at 240 which can engage a spring contact 242 in a circuit leading from a solenoid 172 operating a locking plunger 174 biased upwardly by a spring 176. The locking plunger 174 co-operates with an arm 220 on the second lever 56 to prevent clockwise movement of the lever while the solenoid is energized. The second lever 56 also carries a contact 238 which engages a spring contact 234 to connect a circuit 190, 192 to the ground connection 240 of the switch 242. The circuit 190, 192 leads from a pre-selector switch 112, a switch 152 operated by a centrifugal governor 142 driven from the propeller shaft of the differential so as to be opened when the speed of the propeller shaft falls sufficiently, and an eddy current brake 162 on the propeller shaft. A switch 138 closed by depression of the vehicle clutch pedal may be associated with the limit switch 18 of the motor 13. To change the ratio of the axle drive from low to high, the driver moves the pre-selector switch 112 to the position shown; the speed of the propeller shaft being fairly high, the governor 142 maintains the switch 152 closed. Operation of the electric motor 13 by movement of the switch 112 traverses the nut 44 and pretensions the spring between the levers 52, 56. While the accelerator pedal of the vehicle is maintained depressed, transmission of torque through the two-speed axle drive prevents the ratio establishing member from moving, and thus holds the lever 56 stationary. As soon as transmission of torque is suspended, either by release of the accelerator pedal or depression of the clutch pedal, the ratio establishing member moves to its neutral position, and allows the pre-tensioned spring to turn the lever 56 to the position shown. The grounded contact 246 then engages the contact 242, so that the solenoid 172 is energized to hold the plunger 174 in its locking position engaging the arm 220 on the lever 56. Simultaneously, the contact 238 on the lever 56 engages the spring contact 234 and completes the circuit through the pre-selector switch 112, the governor switch 152, the eddy current brake 162, the contacts 190, 192 and the common ground contact 240. The eddy current brake thus operates to decelerate the rate of rotation of the axle drive propeller shaft, until such time that its speed has fallen sufficiently for the governor 142 to no longer maintain the switch 152 closed. Opening of the switch 152 serves to de-energize the eddy current brake 162 and simultaneously to de-energize the solenoid 172. The pre-stressed spring 58 can then turn the second lever 56 to its final position, pushing the locking plunger 174 downwards against the bias of its spring 176, to complete the establishment of the high ratio. When changing from the high ratio to the low ratio, since the speed of the governor 142 is not sufficient to close the switch 152 and the locking plunger 174 is inoperative, the circuit does not function and the eddy current brake 162 is not energized. Specification 813,031 is referred to.